This invention relates to a surgical suture composed of block polyether-esters which contain (1) a polymeric block of polyalkylene esters and (2) a polymeric block of aromatic dicarboxylic acids or cycloaliphatic acids with short chain aliphatic or cycloaliphatic diols. This surgical suture can be a monofilament, or a twisted or braided multifilament article.
The medical profession is continuously seeking more satisfactory sutures to be used in closing wounds, whether such wounds are incisions from operations, or tears, cuts or abrasions from accidental or other causes. Many materials have been suggested for use as sutures. Sutures are divided into two broad classes, the absorbable sutures, such as catgut or polyglycolic acid sutures, which are absorbed by the body tissues, and nonabsorbable sutures which either remain in the tissues in substantially their original form for prolonged periods or are removed from the skin surfaces after the underlying tissues have been healed. For non-absorbable sutures many materials have been suggested which range from cotton and silk through various synthetic filaments such as polypropylene to stainless steel or nickel or other metallic filaments.
Other things being equal, the medical profession usually prefers the suture which is strongest. In spite of many disadvantages stainless steel has met with considerable acceptance because of its extremely high tensile strength. Such plastic materials as polypropylene are meeting currently with considerable commercial acceptance because of comparatively high tensile strength and because of other advantages over stainless steel.
Additionally, the suture material needs good handling characterstics. The handling characteristics of a suture, as a general statement, are difficult to define but should include a high degree of flexibility.
Handling characteristics include knot strength and knot security. That is, the suture must have such characteristics that a knot can be tied in the suture. Some materials are so brittle that if a suture made from them is knotted, the strength of the suture is markedly reduced. For some materials an overhand knot in a strand can reduce the strength of the strand by a factor of two or more. In addition to knot strength, the suture should have such characteristics that the knot when tied remains in position. Also, the suture should be "throwable" so that when the free end is placed in position by the surgeon it will remain in that position until moved. Similarly, the suture should have such characteristics that it can be thrown or moved from side to side and yet retain the position into which it is thrown.
A surgical suture comprising a high degree of tensile strength with a high degree of flexibility is therefore needed in the medical profession.
A polypropylene monofilament suture is one attempt at solving this need. The tensile strength of this suture is good when compared to stainless steel; and the flexibility of the suture, though better than stainless steel, is still considered to be stiff and springy. See, e.g., U.S. Pat. No. 3,630,205 which is incorporated herein by reference.
A polyurethane suture is another attempt. The primary advantage of this suture is its very high degree of flexibility. However, this has low tensile strength and extremely high elongations at break which make it unsatisfactory for general wound closure methods. See, e.g., U.S. Pat. No. 3,454,011 which is incorporated herein by reference.
Other attempts include the braiding of materials with a high tensile strength but a low degree of flexibility. Dacron.RTM. is an example of a suture with a satisfactory tensile strength after braiding and an increased degree of flexibility. A monofilament suture is generally preferred in most surgical procedures to a braided suture because of the reduced tissue drag of the monofilament. Also, in skin suturing a monofilament suture is generally preferred because it is usually less susceptible to capillary action than a braided suture.
This invention has advantages over these prior art attempts. The suture of this invention shows excellent strength and flexibility as a monofilament. Specifically, the surgical suture of this invention combines the tensile strength of a suture such as a polypropylene monofilament suture, with the flexibility of a braided or polyurethane suture.